The present invention is related to a radio receiver, and in particular to an automobile receiver having a decoder for decoding received digitally coded information transmissions, and more particularly to information transmitted in accordance with an RDS (Radio Data System) System.
German Unexamined Patent Application No. 38 10 180 (incorporate, herein by reference) describes a radio receiver in which digital information, in particular information transmitted according to an RDS, is selectively switched through to an audio output device by an operator (e.g., a driver) through the setpoint input of identifiers. Such an arrangement disadvantageously distracts the driver from current traffic conditions. Further, information regarding the allocation of the identifiers to the geographic location and information regarding the actual location of the radio receiver are required.
German Patent No. 32 14 155 (incorporated herein by reference) describes a radio receiver which selects received messages based on the quality of the transmissions being received and based on a table of transmitter-location coordinates permanently stored in the radio unit. However, with such an arrangement, if the stored data changes with respect to frequency, transmitter identifier, or location, then the information held in the storage device is no longer up-to-date. Further, if as a means of assistance, a transmitter broadcasts the program of another transmitter chain (i.e., relay reception), then the position of the original transmitter may be incorrectly determined.
Moreover, Bosch Technical Reports[Bosch Technische Berichte], volume 8, issue 1/2, pp. 15 through 25, The Transmission of Coded Traffic Information via UKW Radio Transmitters By Means of RDS by Peter Bragas, Fritz Busch, and Claus Mardus (incorporated herein by reference), describes an RDS which transmits standardized texts of traffic messages as coded messages. In such a system, the decoding of the traffic messages and conversion into voice signals takes place directly in the radio receiver.
An RDS Traffic Radio-Communication System is described by the article by Franz Stollenwerk, RDS - A New Service in UKW Broadcasting, in the trade magazine ntz, volume 40 (1987), volume 5, pp. 346-351 (incorporated herein by reference). In such an arrangement, the RDS signal is broadcasted together with the broadcasting program and received via an antenna. The RDS signal is initially demodulated in the receiver by a VHF demodulator and is then biphase- and differential-decoded by the subsequent decoder. This demodulation recovers bit-timing and data signals. The data format of the RDS signal of such a system consists of groups, each group containing four blocks. Each block includes a 16-bit word and a 10-bit check word. The brochure, Specifications of the Radio Data System RDS for VHF/FM Sound Broadcasting, European Broadcasting Union 1984, pp. 11, 12 (incorporated herein by reference) specifies the data format for RDS signals. The application of an RDS signal for transmitting information by means of TMC (i.e., Traffic Message Channel) is described in the specification CENELEC EN 50067 in (RDS) SPB 482, p. 4 (incorporated herein by reference). In that system, a data channel is available for TMC identification in the RDS group 1A, block 3.
In the above systems, a car driver must manually select an RDS. Further, changes in transmitter location, frequency, or identification or relayed reception lead to incorrect determination of the original RDS transmitter. Thus, there is a need for an RDS system in which traffic data is automatically selected and in which the original RDS transmitter can be correctly identified.